Cross-linked high-density polyethylene

The dividing line between TP and TS is not always distinct. Cross-linked TSs are thermoplastic during the initial heat cycle and prior to the chemical cross-linking action. Other plastics may behave like crossed-link high density polyethylene, which normally is a TP but can be cross-linked, by high energy radiation or chemically while being processed, to become a TS called XHDPE (1-3, 8, 9, 11). 

The XL-200 D.O.T.-exempted mini-bulk tank is a reusable, lightweight 200 gal tank system for hazardous liquids. Rotationally molded of cross-linked high-density polyethylene (XLPE), the XL-200 has superior resistance to impact and stress-cracking and is compatible with a wide range of chemicals (see chemical resistance summary). It s strong over a wide temperature range, from -20° to -H60°F (-29° to -i-71°C). 

LDPE—Low-Density Polyethylene HDPE—High-Density Polyethylene XLPE—Cross-linked High-Density Polyethylene PP—Polypropylene... 

In this study, poly(acrylic acid) (poly(AA)), poly(acrylic acid-co-vinylsuHonic acid) (poly(AAVS)) or poly(acrylamide tert-butyl sulfonic acid) (poly(ATBS)) was used as the filUng polymer, and porous polytetrafluoroethylene (FI FE) [17, 18], porous cross-linked high-density polyethylene substrate (CLPE) or a porous polyimide substrate (PI) was used as the substrate. Polyacrylic acid is a weak acid and the poly(AAVS) copolymer has a sulfonic acid group of 0.7 nunol g" -polymer, because the vinylsulfonic acid content in the copolymer is 5 mol%. Poly(ATBS) has a 4.5 mmol g -polymer sulfonic acid content. 

There are three basic types of polyethylene foams of importance (/) extmded foams from low density polyethylene (LPDE) (2) foam products from high density polyethylene (HDPE) and (J) cross-linked polyethylene foams. Other polyolefin foams have an insignificant volume as compared to polyethylene foams and most of their uses are as resia extenders. 

Blends of isobutylene polymers with thermoplastic resins are used for toughening these compounds. High density polyethylene and isotactic polypropylene are often modified with 5 to 30 wt % polyisobutylene. At higher elastomer concentration the blends of butyl-type polymers with polyolefins become more mbbery in nature, and these compositions are used as thermoplastic elastomers (98). In some cases, a halobutyl phase is cross-linked as it is dispersed in the polyolefin to produce a highly elastic compound that is processible in thermoplastic mol ding equipment (99) (see Elastomers, synthetic-thermoplastic). ... 

Anbarasan, R. Babot, O. Maillard, B. Cross-linking of high-density polyethylene in the presence of organic peroxides. J. Appl. Polym. Sci. 2004, 93, 75-81. 

High Density Polyethylene (HDPE). The preferred method of evaluating HDPE was found to be the time to cross link at 220 0 using the Brabender apparatus, as is made evident by the rapid increase in torque. Determining melt viscosity by multiple extrusion showed only small differences compared to the base polymer. 

Kolesov and Radusch prepared peroxide cross-linked binary and ternary blend SMPs from high density polyethylene and two ethylene-l-octene copolymers with medium and high degrees of branching [47]. The blends were prepared by a melt mixing and subsequently are cross-linked with 2 wt% of liquid peroxide 2,5-dimethyl-2,5-di-(tertbutylperoxy)-hexane at 190°C. The blends showed multiple shape memory behavior that appeared only at consequent stepwise application of convenient programming strains and temperatures. Obviously, that is caused by multiple melting behavior of these blends with many poorly separated peaks. 

The membrane prepared by cross-linking a pore-filling graft polymerization of methyl acrylate onto high density polyethylene (HDPE) was used to compare the pervaporation and RO of a chloroform-n-hexane mixture (Kai et al. 2005). Both the permeation rate and the separation factor in RO are lower than those in PV, but considering the effect of the osmotic pressure present in RO, the membrane showed a reasonable separation performance in RO. 

In direct fluorination of powdered high-density polyethylene with the gas, diluted with helium or nitrogen, the accompanying exotherm causes partial fusion. In addition, there is some destruction of the crystalline regions [137]. On the other hand, fluorination of single crystals of polyethylene can result in fluorine atoms being placed on the carbon skeleton without disruption of the crystal structure. The extent of cross-linking, however, is hard to assess [138]. The reaction has all the characteristics of free-radical mechanism [139] ... 

Tang (134) studied the effect of the interaction between carbon black and the polymer on electrical behavior. The absorption of polymer on the carbon black surface may be physical or chemical. The latter is caused by free-radical reaction between the polymer and carbon black, and it can occur during radiation or the preparation of the composite. In carbon-black-lilled high density polyethylene, the cross-linked network of the pol5uner restricts the freedom of movement of carbon black. The free-radical reaction enhances the binding force between the polymer and carbon black. 

Composites of banana, hemp, and agave with high-density polyethylene resin were separately prepared in different ratios 60 40, 55 45, 50 50, and 45 55 (wt/wt). These fibers were also treated with maleic anhydride, and the effect of maleic anhydride on surface resistivity and volume resistivity of wood polymer composites was studied. The surface resistivity decreased with an increase in fiber content in the composites, while volume resistivity increased. The maximum surface resistivity and volume resistivity were observed in the untreated banana fiber composite, while minimum surface resistivity and volume resistivity were found in the maleic anhydride-treated agave fiber composite. The decrement in volume resistivity and surface resistivity was due to the increase in cross-linking between the polymer and fiber by treatment with maleic anhydride. 

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